\section{Challenges to ICN}
\label{chap:challenges}

In the following sub-sections, we will give an overview of some of the challenges that face ICN. \bigskip

\noindent From the Internet users point of view the main interest is on data exchange (such as multimedia applications) in a high quality and performance with a low access cost, although they do not take into consideration what kind of technology is used for these purposes. New technologies have helped to increase bandwidth availability of the network and reduce the access cost, which has allowed developing many new applications and brought more new users to the Internet. This scenario has increased ISPs profit and their interest in the development of ICN because it is a promising future Internet infrastructure \citep[p. x]{BRITO}.\bigskip

\noindent Many ICN proposals and solutions for different art of future Internet demands and problems have been discussed and experienced, but there are still some open issues and challenges for deploying ICN architecture. In this section we will give a brief account for the following: naming, routing, caching, security, mobility, applications, and economic issues.

To make ICNs a viable and reliable technology for deployment, it is obvious that these issues (among others) will need to be addressed.

\subsection{Naming}
Information-Centric Networking is based primitively on content naming, and that is well focused by all ICN proposed architectures. It is crucial to have a correct understanding of the naming because it is intricately linked with resolution and ID-based routing. One of the main points in this understanding is how to come up with a naming architecture that can provide global information of the named content of objects and at the same time assure that this information has mobility and can be easily looked up. \citep[p. 43]{BRITO} \bigskip

\noindent \textit{``Names should have global uniqueness, security, location independent and human-friendly. In practice, there is no single mechanism that satisfies these requirements.''} \citep[p. 51]{BRITO} The problem is that the proposed architectures of ICN have implemented it differently, and \textit{``there is no consensus on which approach presents more advantages. [...] Therefore, naming mechanisms for ICNs are still an important challenge to be investigated.''} \citep[p. 51]{BRITO}

\subsection{Routing}
Some of ICN routing mechanisms are discovery of closest copy of the content among multiple copies that are distributed on the network, scalability, retrieval locality and security. 
\bigskip

\noindent TRIAD has made one out of several studies that have analysed the scalability of name-based ICN routing mechanisms. This particular routing mechanism is especially challenging because of its massive size of routing tables and because of the difficulty summarizing all of these names. In continuation of this the difficulties of aggregating names in ICNs is cause by the naming approach that ICN architecture has adopted. ICN routing mechanisms therefore need to have a better overview over the huge amount of orders of the expected namespace than of the current address space. This aspect of how to manage the content state is not yet explored and therefore research in this field is needed. \citep[p. 52]{BRITO}\bigskip

\noindent \textit{``No single mechanism provides all of them. In fact, it is difficult to provide even a few of them simultaneously.''} \citep[p. 52]{BRITO} \textit{``Several desired properties of routing mechanisms are not currently addressed by any ICN architecture proposed.''} \citep[p. 57]{BRITO}

\subsection{Caching}
The main goal of ICN caching is to improve the network performance for content distribution. It is first and foremost accomplished by using the bandwidth in the core of the network efficiently to reduce the content delivery delay, and secondly by implementing cache in all routers, 'forming a network of caches' to have multiple copies of the same content, which reduce the traffic and the load in the network. ICN have implemented cache in all of their routers on the network, which in turn have given them universal storage of content on the network. \citep[p. 58]{BRITO}

\begin{quote}
\textit{``[I]n some ICN architectures, the content is divided into smaller pieces of the same size, named content chunks, and thus caches store chunks instead of storing the entire contents. Content size can have a significant impact on the performance of the content storage system [...]. Therefore, in architectures such as CCN, using a fixed size for chunks simplifies the problem.''} \citep[p. 59]{BRITO}
\end{quote}

\subsection{Security}
Trust in the content itself is the way ICN security is build of. It is not dependent of the origin or location of the content. There are some problems that should be solved to make content trustful, like verify the integrity of the content and how relevant it is to the requested one. But the main ICN security problem is the privacy issue because of using content names for forwarding and routing tasks. \textit{``In ICNs, routers have direct access to the users content requests. Therefore, if the router is compromised, the attacker is able to monitor the requests submitted by the users and know exactly their interests. This approach allows not only for discovering user profiles but also for monitoring the user's daily life. [..] Although security is an important research area, efforts to address the main problems are still quite limited and insufficient.''} \citep[pp. 69-73]{BRITO}

\subsection{Mobility}
ICN aims to improve mobility support; \textit{``in this context, mobility involves the physical and/or topological re-location of a device in regards to its access network.''} \citep[p. 1]{TYSON} \bigskip

\noindent Having an active communication while a user is moving requires extra effort to ensure a suitable quality of service (QoS). This is because the connection between the moving user and the network will go through several base stations, which means that network re-configuration must take place to manage these changes and to keep continuous communication with the user. \textit{''[M]obility should therefore not result in lost data or extended periods of disconnection.''} \citep[p. 1]{TYSON}\bigskip

\noindent Mobility in the current Internet has always been considered \textit{``due to the complexity of managing changes in a node's geographic and topological location''}. Various overlaying protocols and Mobile IP are defined to manage this issue. In ICN \textit{``the core problems relating to this are not resolved; instead, the goal posts are simply shifted. As such, there are still a number of important research challenges that remain in this domain.''} \citep[p. 2]{TYSON}
\bigskip

\noindent Because some ICN architectures require to follow the same routing path for requesting and sending messages between users and network, an investigation still need to be achieved for being able to \textit{``sending a request from one location but receiving the replay at another[, and] if ICNs are to be deployed in dynamic mobile environments, this is an extremely important research issue to address.''} \citep[p. 5]{TYSON}

\textit{Applications}
ICN is still in research domain, where several questions have not solved yet. In such unclear environment new applications to the paradigm of ICN is a big challenge. \textit{``Although information-centric networks increase the efficiency of content distribution applications, it is necessary to investigate the performance of typical conversational applications such as electronic mail and voice transmission over IP networks (Voice over IP), since in ICN content is routed based on its name rather than on its IP address.''} \citep[p. 78]{BRITO}

\subsection{Economic Issue}
The current Internet business model is based on connectivity. It works by forwarding packets to the users, who pay for the Internet subscription to their local ISPs . Various ICN architectures are proposed, and some have been experimented with prototypes in test beds, like CCNx1 and PURSUIT. But to use these proposals on a large scale, a definition of an incentives economic model is a must to engage and encourage involved stakeholders, current network operators and providers to change the current well-working business model and to ensure profitability for their activities to adopt to ICN architecture, which is another challenge for deploying of ICN. \citep[pp. 83.84]{BRITO}

